This function tests whether the correct error message is thrown.
omxCheckError(expression, message)an R expression that produces an error
a character string with the desired error message
Arguments ‘expression’ and ‘message’ give the expression that generates the error and the message that is supposed to be generated, respectively.
The OpenMx User's guide can be found at <https://openmx.ssri.psu.edu/documentation>.
omxCheckWarning
omxCheckWithinPercentError,
omxCheckIdentical, omxCheckSetEquals,
omxCheckTrue, omxCheckEquals